;(function (doc, initTools) {
  var oCalculator = doc.getElementsByClassName('J_calculator')[0],
      oResult = oCalculator.getElementsByClassName('result')[0],
      oInputs = oCalculator.getElementsByTagName('input'),
      oBtnGroup = oCalculator.getElementsByClassName('btn-group')[0] 
  
  var init = function () {
    bindEvent()
  }

  function bindEvent () {
  	oBtnGroup.addEventListener('click', onBtnClick, false)
  }

  function onBtnClick (ev) {
  	var tar = initTools.getTarget(ev),
  	    tagName = tar.tagName.toLowerCase()

  	if (tagName === 'button') {
      var method = tar.getAttribute('data-method'),
        fVal = initTools.digitalize(oInputs[0].value),
        sVal = initTools.digitalize(oInputs[1].value)
      renderResult(initCompute[method](fVal, sVal))
  	}
  }

  function renderResult (result) {
  	oResult.innerText = result
  }
  
  init()

})(document, initTools)







